clutch slave cylinder thread size...

[swifty]

Any of you knowledgeable folk out there know what the internal thread size is for the clutch slave cylinder? (It s a 7/8" cylinder from Witors if that makes any difference)

Reason I ask is that I have a Spitfire six that I have transplanted the big six gearbox into and need to mate the Spitty clutch master cylinder to the big six slave, and typically they ain't the same, so I need to change the slave union

[Alan Chatterton]

Hi swiftly!

Sorry, I don't know the answer but I'm sure someone will be along soon who does!

Just wanted to say hi, haven't heard from you in a while. Still got the pi?

[djw113uk]

either 3/8" or 7/16"

[tony]

Normally 3/8" UNF.
Tony.

[johnconradlee]

Presumably you mean the pipe thread?
It's NPT or JIC I think (more 'orrid American threads...). I'm certain it's not BSP.

[swifty]

Yes Alan, still got my 2500 - the bad news is it's developed a dreadful crank end float (so big is the movement I fear one of the thrust washers has dropped out) The good news is I have a spare engine waiting to go into it (that is tuned to c.150bhp ) although what with me working on Mrs Swifty's SPIT 6 it is in the queue of things to be done

And yes, John, that's the thread I mean - I have an adaptor from a Goodridge braided Clutch line I bought for a Dolly Sprint years ago, and that fits. (although,of course that is too short and the other end is too big to fit the master cylinder ) The threads are quite chunky, and my prior interrogation of t'internet had thrown up that it could be an NPT thread, but does it come in particular sizes (ie 7/16 NPT, 3/8 NPT, etc or equivalents)

I think I might need an adaptor with a female 7/16 and a male NPT...

[Alec]

Hello Swifty,

I would be surprised if it's a pipe thread (NPT) as the brake lines are swaged to seal, either flare or bulb. Most of the 2000 range is 3/8" UNF but as the clutch line is 1/4" as opposed to 3/!6" it's possible that it is 7/16" UNF?

Alec

[Alan Chatterton]

Dropped thrusts are easy to put back in you know, no need to change engine. But 150bhp is a good enough reason I guess!

[johnconradlee]

After a bit of research I think Alec is right, they're 7/16" JIC for the clutch and 3/8" JIC for the brakes (which is a UNF thread with a cone or pipe flare on the end to make it seal).
The irritating NPT thread is on the oil pressure switch (I knew there was one somewhere).
There is a 7/16" female to 3/8" male adaptor (I think, assuming my thread sizes are right - either way bigger female to smaller male) as part of the normal Triumph 2000 clutch hydraulics that screws into the clutch master (the hexagonal bit on the master cylinder should unscrew - assuming you have the same clutch master that had). You could I suppose borrow it off the other car, check it fits, then take it to your local hydraulic hose shop and ask if they can get you another one?

[Mike Stevens]

Dropped thrusts are easy to put back in you know, no need to change engine

True, but if the crank has moved right forward to then thrust against the block, it will make some nasty noises and likely damage both crank and block.

I bought a 'cheap' TR6 engine in that state many years ago. My local engineering company trued up the crank damage and made up special brass (or maybe phospher-bronze) thrusts that were screwed onto the block and main bearing cap. They are so big they will never wear! It wasn't too expensive either.

I still have this engine, complete with SAH 357 Cam which may just find its way into the current PI!

Cheers,
Mike.